Method of making dual lumen catheters

ABSTRACT

A method of making a dual lumen catheter which is a unitary, elongated, flexible catheter tube that is substantially circular in cross-section. The catheter tube has an outer wall member forming a tube having a proximal end and a distal end portion adapted for insertion within a vein or artery of a patient. The outer wall member defines first and second coaxial lumens that are separated by an inner common support wall which is substantially circular and joins the outer wall. The first lumen extends longitudinally between the opposed distal and proximal ends of the catheter tube and terminates coextensive with the distal end portion of the catheter tube. The second lumen extends longitudinally from the proximal end of the catheter tube and terminates proximal to the distal end portion of the catheter tube. The second lumen is crescent-shaped in cross-section and substantially surrounds the first lumen. The cross-sectional areas of the first and second lumens are approximately equal. Each of the first and second lumens are totally smooth internally, thereby containing no ridges or connections which can promote formation of blood clots or cause hemolysis or damage to red blood cells during dialysis. The catheter tube is secured at its proximal end to the distal end of a hollow hub assembly.

This application is a division of application Ser. No. 08/203,126 filedFeb. 28, 1994 and now U.S. Pat. No. 5,380,276.

FIELD OF THE INVENTION

The invention relates in general to catheters, and more specifically todual lumen catheters.

BACKGROUND OF THE INVENTION

Multilumen catheters are used to simultaneously infuse a plurality offluids into a patient, the separate lumens of the catheters preventingfluids from mixing during the infusion process and before the fluidsenter the patient's body. Preventing fluid mixing is particularlyimportant where the simultaneously infused fluids are chemicallyincompatible.

Multilumen catheters are also useful for simultaneous infusion of fluidsand withdrawal of samples of the patient's body fluids, thus avoidingthe need for insertion of multiple separate catheters into the patient.

SUMMARY OF THE INVENTION

The invention features a dual lumen catheter comprising a unitary,elongated, flexible catheter tube that is substantially circular incross-section, the tube having an outer wall member forming a tubehaving a proximal end and a distal end portion adapted for insertionwithin the vessel of a patient, the outer wall member defining first andsecond coaxial lumens that are separated by an inner common support wallwhich is substantially circular and joins the outer wall, the firstlumen extending longitudinally between the opposed distal and proximalends of the catheter tube and terminating coextensive with the distalend portion of the catheter tube, the second lumen extendinglongitudinally from the proximal end of the catheter tube andterminating proximal to the distal end portion of the catheter tube, thesecond lumen being crescent shaped in cross-section and substantiallysurrounding the first lumen, the cross-sectional areas of the first andsecond lumens preferably being substantially equal. As used herein,"substantially equal" means approximately or nearly identical, whichwill generally be within 90% of being identical.

Each of the lumens is totally smooth internally, thereby containing noridges or connections which can promote formation of blood clots orcause hemolysis or damage to red blood cells, thereby inhibiting ormaterially reducing the likelihood of these occurrences during dialysis.

As heretofore noted, the catheter tube is secured at its proximal end tothe distal end of a hollow hub assembly. The hub assembly is divided orsplits at its proximal end into two hub segments each of which isconnected to a tubing extension. The hub assembly and tubing extensionsare unitary with the catheter tube with one of the tubing extensionsbeing in fluid communication with the first lumen and the other tubingextension being in fluid communication with the second lumen.

In preferred embodiments, the dual lumen catheter further comprises aflexible collar extending around and from the proximal end of thecatheter tube and terminating at or proximal to the distal end of thehub, the collar comprising a material that is more rigid than thecatheter tube and thus offers support for the tube, providing a strainrelief which serves to prevent kinking.

The dual lumen catheter further comprises at its distal end one or moreport holes extending from the first or second lumen through the outerwall of the catheter tube; preferably, two side port holes enter intothe circular first lumen and six side port holes enter into thecrescent-shaped second lumen.

The dual lumen catheter may further comprise a releasable clamp fixed oneach tubing extension.

Preferably, at least one of the lumens of the catheter is in fluidcommunication with a source of liquid to be introduced into the patientthrough the catheter. The dual lumen catheter, including the cathetertube and hub assembly, is preferably constructed of a semi-rigidmaterial which is heat formable, e.g., polyurethane.

The invention also includes methods of kidney dialysis andplasmapheresis using the catheter of the invention.

In one method, the distal end of a catheter of the invention isimplanted in a blood vessel, i.e., a vein or artery, such that thelumens of the catheter are in communication with fluid in the bloodvessel so as to permit passage of fluid from the blood vessel throughthe lumen; fluid is then removed from the blood vessel via one lumen andtreated to remove toxic metabolic waste; and the fluid is thenre-infused into the blood vessel via the other lumen of the catheter.

According to another kidney dialysis method of the invention, a dialysissolution is infused into a patient's peritoneal cavity via the one lumenof a catheter of the invention, the dialysis solution is allowed toremain in the patient's peritoneal cavity for a time sufficient forblood impurities to be removed from the patient's blood by diffusionacross the peritoneal membrane into the dialysis solution, and thedialysis solution is then drained from the peritoneal cavity via theother lumen of the catheter tube.

Catheters of the invention are particularly well-adapted for acute carekidney dialysis in that they comprise a unitary piece of flexible, i.e.,semi-rigid, structurally stable material, such as a thermoplasticmaterial, e.g., polyurethane. The internal surfaces of a catheter of theinvention are completely smooth and have no nicks, crevices or jointsupon which tissues in body fluids, particularly red blood cells, mayaccumulate and coagulate. This complete smoothness is attained byconstructing the catheter tube and hub assembly, including hub joint andtube extensions which join to the dialysis tubing, by insert-molding orinjection molding using heat but no solvents. Insert-molding into aunitary piece provides lumens which are totally smooth internally, i.e.,contain no ridges, connections, etc., which can promote problems whichare common in dialysis, e.g., formation of blood clots and causehemolysis or damage to red blood cells. In addition, because cathetersof the invention are unitary, there is a reduced risk of tip breakageupon insertion or removal of the catheter from the patient.

Other important advantages of catheters of the invention include greatlyreduced susceptibility of the catheter tube to kinking and bending, thusgreatly reducing risk to the patient of interrupting the dialysisprocess and potentially forming clots at the site of a kink. Catheterdevices of the prior art which include a straight septum conferincreased susceptibility to kinking in both directions. Some embodimentsof the catheter of the invention include a strain-relieving collar whichserves to further support the catheter tube and thus completely preventbending of the tube during use.

The novel features as well as the nature and objects of the inventionwill be more fully understood from the following detailed descriptiontaken in conjunction with the accompanying illustrative drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of the dual lumen catheter of thepresent invention;

FIG. 2 is a side section view of the invention along Line 2-2' of FIG.1.;

FIG. 3 is a cross-sectional view of the catheter tube of FIG. 1; and

FIG. 4 is a bottom plan view of a portion of the catheter of FIG. 1,partially broken away.

DETAILED DESCRIPTION OF THE INVENTION EXAMPLE I

Referring to FIG. 1, there is shown the preferred embodiment of the duallumen catheter of this invention, generally designated as 1. The duallumen catheter 1 has an elongated, flexible catheter tube 10 with atapered distal end 11 capable of insertion into and being fedlongitudinally within a blood vessel of a patient. Dual lumen catheter1, including tube 10, hub assembly 17, and tube extensions 23,24, ismade by insert molding or injection molding using a thermoplasticmaterial, e.g., polyurethane. Thus, the catheter 1 is a unitary piece offlexible, i.e., semi-rigid, material which is completely smoothinternally.

Those skilled in the art will appreciate that the tapered distal end 11is conventionally introduced over a guide wire which has previously beenplaced within the blood vessel. Those skilled in the art will alsounderstand that the common method to accomplish the placement of theguide wire within a blood vessel is the well-known "SeldingerTechnique". After penetration by the needle, the catheter tube 10 isthen fed longitudinally over the needle for a sufficient length so as tointroduce within the blood vessel the lateral side ports 13, 15 openingto the interior of the catheter tube 10. The tube 10 is connected at itsproximal end 12 to the distal end 16 of a fluid-conveying hollow hubassembly 17. Hub assembly 17 is divided or splits at its proximal end 18into two integral hub segments 21,22 which are connected to tubingextensions 23,24 respectively. The tubing extensions 23,24 are in turnconnected at their proximal ends to adapters 27,28 respectively forattachment to a suitable device or fluid source. As shown in FIG. 1,adapters 27,28 are provided with Luer lock caps 29,30 respectively, forcovering the adapters when they are not in use connecting the tubingextensions. Also as shown in FIG. 1, conventional clamps 25,26 areprovided to open and close tubing extensions 23,24 respectively, asdesired.

In the preferred embodiment of the invention, catheter tube 10 isencased at its proximal end 12 by a collar 19 which serves to supporttube 10, provides strain relief and further prevents bending during use.In addition, while not necessary to the practice of the invention,suture tab 31 having a pair of holes 32 is preferably provided forsecuring the catheter to the patient by means of a suture.

Referring now to FIGS. 2-4, there is shown to be two longitudinallyextending lumens 5,6 within the catheter tube 10. FIG. 3 shows thegenerally circular cross-section of the catheter tube 10 with the twolumens 5,6 contained therein and separated by septum 8. Lumen 5 iscircular in cross-section, whereas lumen 6 is crescent-shaped incross-section. Thus, the catheter contains two conduits corresponding tolumens 5 and 6. Circular lumen 5 will be most often used as a "venous"lumen, i.e., for returning clean blood to the patient, whereascrescent-shaped lumen 6 will be used as an "arterial" lumen, i.e., toremove blood from the patient via the side ports.

As seen, a novel feature of this invention is that the cross-sectionalarea of lumen 5 is substantially equal to the cross-sectional area oflumen 6, and thus lumens 5 and 6 are capable of holding a substantiallysimilar volume of fluid. For purposes of the illustration, the cathetertubes may be of several sizes, e.g., 11, 10, or 8.5 french,corresponding to an outside diameter of on the order of 0.151 inch,0.131 inch, or 0.114 inch, respectively. The circular lumen 5 will thushave an internal diameter of 0.079 inch in the size 11 french cathetertube. The size 11 french catheter will be useful primarily for insertioninto an adult vessel for dialysis, the size 10 french catheter forinsertion into a vessel of a smaller adult or a teenager, and the size8.5 french catheter for insertion into a vessel of a child.

Catheter tube 10 terminates at distal end 11. Lumen 5 terminates throughport 9 coextensive with the distal end 11, whereas lumen 6 terminates atportion 14 proximal to distal end 11.

Catheter tube 10 also includes side ports which allow for fluidcommunication between lumen 5 or lumen 6 and the external environment.Side ports 13 are separately spaced in the side wall of catheter tube10. These lateral side ports 13 enable entry and discharge of fluid fromlumen 6, as lumen 6 does not terminate in a port. Catheter 10 may alsoinclude side ports 15 which are spaced apart near the distal end 11 ofthe catheter and allow for fluid exchange between lumen 5 and theexternal environment. Fluids may be infused or blood withdrawnefficiently through lumen 5 through the end port 9 and side ports 15. Inone embodiment of the invention, the distal end of catheter tube 10 willinclude two side ports 15 entering lumen 5, the circular lumen, and sixside ports 13 entering lumen 6, the crescent-shaped lumen.

In accordance with the present invention, the dual lumens 5,6, aretotally independent and non-communicative with one another so that fluidcarried therein will not mix prior to entering the bloodstream.

The dual lumen catheter of the invention is constructed by insertmolding as follows. Initially, the dual lumen tube is formed, e.g. byextrusion through a die. Side holes are then drilled through the outerwall at the distal end of the tube to reach the crescent or circularlumen. A mandrel is placed in the circular center lumen and the tip ofthe tube is heated so to allow the crescent-shaped lumen to collapsearound the tip. Thus, the crescent lumen will terminate proximal to thedistal end of the catheter tube. The thus-fabricated tube is thenconstructed as a unitary piece with the hub assembly as follows. Pinsare inserted into the proximal ends of the crescent and circular lumens,the pins being shaped crescent and circular in cross-section,respectively. The proximal ends of the two pins diverge into a Y-shapeto mimic the Y-shape of the hub assembly, as shown in FIG. 1. Extensiontubing of a suitable size is inserted over the proximal end of each pinto within a short distance of the proximal end of the tube 10. Thecatheter tube and pins are then placed in a mold. A suitable polymericmaterial such as polyurethane of a somewhat stiffer nature after moldingis then heated and injected into the mold to form the hub assembly as aunitary piece with the catheter tube and extension tubing. Upon cooling,the pins are removed, leaving channels which form the lumens, hub andextension tubing. Finally, a clamp is placed around each extension tubeand luer fittings are solvent bonded at each extension tube end.

Depending on the source to which the tube extensions 23 and 24 are incommunication, the dual lumen catheter of this invention may also beemployed in per se known manner to continuously draw and return blood toa patient, monitor blood pressure and/or obtain a blood sample and/orinfuse fluid into the blood vessel of the patient.

In use, a guidewire is first introduced into the desired blood vessel inthe direction of the flow of blood, e.g. by the aforementioned"Seldinger Technique". Thereafter, the distal end 11 of the cathetertube 10 is fed into the puncture over the guide wire the desireddistance until all the ports 13,15 are fully within the blood vessel.The luer-lock caps 29,30 are removed and the catheter tube 10 placed influid communication via extension tubings 23,24 with the desired deviceand/or fluid source for administration to the patient. As is wellunderstood, when drug syringes are employed, for example, the drugs areinjected into adapters 27,28 where they then flow through extensiontubings 23,24 and then through hub assembly 17 into the dual lumens 5,6respectively for introduction within the blood vessel through the distalportion of the catheter tube.

From the foregoing description it will thus be seen that the presentinvention provides a novel dual lumen catheter satisfying the objectivesof the invention. The advantage of reduced kinking is solved by thecurved nature of the septum 8, which renders the tube less susceptibleto bending.

It will be appreciated that various changes may be made withoutdeparting from the scope of the invention herein contemplated. Forexample, while for purposes of illustration the invention has beendescribed with reference to ports in each of the conduits 5,6, it iscontemplated that a lesser or greater amount of ports may be utilized ineach of the conduits, i.e. each may have but a single port or aplurality of ports greater than the two shown in the drawings.

EXAMPLE II

The methods and apparatuses of the invention are particularly useful inthe treatment of patients experiencing renal disease, such as partial ortotal kidney failure. End stage renal disease currently affects over100,000 patients in the United States, and over 400,000 patientsworldwide. The patient load for this disease continues to grow at aseven percent annual rate.

Kidney failure may be acute or chronic. Acute failure may be caused bytrauma, surgery, or disease but is time-limited as the patient heals.Chronic failure is permanent and will continue for the long term untilthe patient dies. Treatment for chronic or end stage renal diseaseconsists of kidney transplant procedures or dialysis. Kidney transplanttherapy is limited by the availability of suitable organ donors, anddialysis becomes the only remaining treatment (U.S. Pat. No. 5,151,082Sep. 29, 1992 Gorsuch, et al.) for chronic kidney failure.

Dialysis is the process of removing metabolic waste products from theblood, a function performed by the natural kidney in a healthycondition. These waste products include salts, urea, creatinine, uricacid, and water. The substances are removed by diffusion across amembrane to a dialysate fluid which has a low concentration of thesubstances.

Dialysis takes place either by continuous ambulatory peritoneal dialysisin which the membrane used is the vascular membranes of the body in theperitoneal cavity, or hemodialysis in which an artificial membrane isused. In hemodialysis, blood is removed by placement of the catheter inan artery or vein, passed over one side of an extracorporeal porousdialyzer membrane, and returned to the body via the artery or vein intowhich the catheter is introduced. The membrane is made of cellulose oranother suitable material. Dialysis fluid is passed over the other sideof the dialyzer membrane and the metabolic waste products pass throughthe porous membrane from the blood to the dialysate by the process ofdiffusion. The pores in the membrane are sized such that the wasteproducts pass through the membrane but other blood components such ashemoglobin, albumin, gamma globulin, virus and bacterial bodies, are toolarge and cannot pass through the pores. Excess water is passed throughthe membrane by an ultrafiltration process (U.S. Pat. No. 5,151,082 Sep.29, 1992 Gorsuch et al.) in which a positive pressure gradient iscreated between the blood and the dialysate on opposite sides of themembrane.

Although hemodialysis is widely used as a treatment for kidney failure,there are significant problems associated with the procedure. Forexample, the removal of whole blood from the body, followed byprocessing and returning that blood, causes clotting, infection, anddamage to the cells, as well as damage to proteins and other bloodcomponents. Therefore, it is important that the catheter apparatus usedin the procedure be as efficient as possible in removing blood from andreinfusing cleansed blood to the patient, such that the flow of fluidsout of and back into the patient is as continuous as possible andminimizes the opportunity for infection, clotting, and tissue trauma.

Another treatment of renal disease is through a procedure known asintermittent peritoneal dialysis. In this procedure, a dialysis solutionis infused into the patient's peritoneal cavity by means of tubing and acatheter. The peritoneum, which defines a peritoneal cavity, containsmany small blood vessels and capillary beds which act as a naturalsemipermeable membrane. The natural membrane may be contrasted with theartificial membrane used in hemodialysis. In both cases, however,impurities and toxins in the blood are removed by diffusion across amembrane such as a cellulose membrane of the artificial kidney or aperitoneal natural membrane of the peritoneal cavity. Dialysis solutionsremain in the patient's peritoneal cavity in intermittent peritonealdialysis for a time sufficient for blood impurities to be removed bydiffusion across the peritoneal membrane into the dialysis solution. Theimpurity containing dialysis solution then is drained from theperitoneal cavity by means of a catheter and tubing and a fresh supplyof dialysis solution is infused. Again, it is important that thecatheter be adapted so as to efficiently and continuously infuse andremove fluids to and from the patient with a minimum of trauma.

Thus, in use in kidney dialysis, the dual lumen catheter of theinvention 10 is inserted at end 11 into the subclavian artery, femoralvein, or jugular vein of the patient such that ports 13,15 are containedwithin the vein and thus are in fluid communication with the vein orartery. Luer lock caps 29,30 are removed from adapters 27,28,respectively, and connected to the dialysis machine via tubingextensions (not shown). When dialysis is commenced, clamps 25,26 arereleased to allow flow of fluid through tubing extensions 23,24. Thedual lumen catheter of the invention is particularly useful for kidneydialysis in that it is flexible along its length by virtue of the curvedseptum 8. Thus, the catheter tube will not kink or buckle during use,and will not expose the patient to such risks as damage to red bloodcells potentially resulting in formation of blood clots in the reinfusedblood. During dialysis, venous blood is removed from the patient vialumen 6 and cleansed and returned to the patient via lumen 5. Thecatheter of the invention, because it is a unitary piece of semi-rigid,structurally stable material, is completely smooth internally in bothlumens, thus further reducing the risk damage to red blood cells andclotting. In addition, because of its unitary construction, there islittle danger of that the distal tip of the tube will break off duringinsertion into or removal from the patient.

Alternatively, catheters of the invention may be used for another methodof dialysis described above, i.e., peritoneal dialysis. According tothis method of the invention, a dialysis solution is infused into apatient's peritoneal cavity via lumen 5 of the catheter tube describedherein, the dialysis solution is allowed to remain in the patient'speritoneal cavity for a time sufficient for blood impurities to beremoved from the patient's blood by diffusion across the peritonealmembrane into the dialysis solution, and the dialysis solution is thenremoved from the patient's peritoneal cavity via the lumen 6 of thecatheter tube. For either of the above methods, the invention is notlimited to fluid infusion or removal via lumens 5 and 6 respectively,but may also be performed using lumen 5 for fluid removal and lumen 6for fluid infusion.

Accordingly, it is to be understood that the foregoing description andaccompanying drawings are merely illustrative of the preferredembodiment of the dual lumen catheter of the present invention, and thatno limitations are intended other than as defined in the appendedclaims.

We claim:
 1. A method for making a unitary dual lumen catheter and hub,comprising:(a) providing a dual lumen catheter comprising:a unitary,elongated, flexible catheter tube that is substantially circular incross-section, said tube having an outer wall member forming a tubehaving a proximal end and a distal end portion adapted for insertionwithin the vein of a patient, the outer wall member defining first andsecond lumens that are separated by an inner common support wall whichis substantially circular and joins said outer wall, said first lumenextending longitudinally between the opposed distal and proximal ends ofthe catheter tube and terminating coextensive with said distal endportion of said catheter tube, said second lumen extendinglongitudinally from the proximal end of the catheter tube andterminating proximal to said distal end portion of said catheter tube,said second lumen further comprising adjacent said distal end a porthole extending through said outer wall, said second lumen being crescentshaped in cross-section and substantially surrounding said first lumen,the cross-sectional areas of the first and second lumens beingapproximately equal, each of said first and second lumens being totallysmooth internally, thereby containing no ridges or connections which canpromote formation of blood clots or cause hemolysis or damage to redblood cells during dialysis; (b) inserting within said proximal tube enda support shaped to fit within said first and second lumens, saidsupport extending from said tube proximal end in a branchedconfiguration; (c) placing said dual lumen catheter with insertedsupport of step (b) into an insert mold shaped to hold said catheter atsaid catheter distal end and to hold a softened material around saidbranched configuration at said catheter proximal end; (d) placing asoftened material in said insert mold around said branched configurationand allowing said material to harden to form a branched hub integralwith said catheter proximal end; and (e) removing said support.
 2. Themethod of claim 1, further comprising the step, prior to said step (d),ofplacing extension tubing over the extended branched configuration ofsaid support such that, upon performing said step (d), said branched hubis integral with said catheter proximal end at one end and saidextension tubing at the other end.
 3. The method of claim 2, whereinsaid support comprises a pin which is branched at its proximal anddistal ends, the distal end branch being shaped crescent and circular incross-section so as to slide within said dual lumen catheter tube, theproximal end branch being Y-shaped.
 4. The method of making a unitarydual lumen catheter having a hub comprising the steps of:(a) initiallyforming a dual lumen catheter having a unitary, elongated flexible tubethat is substantially circular in cross-section, the tube having anouter wall member forming a tube having a proximal end and an opposeddistal end portion adapted for insertion within the vein of a patient,the outer wall member defining first and second lumens that areseparated by an inner common support wall which is substantiallycircular and joins the outer wall, the first lumen extendinglongitudinally between the opposed distal and proximal ends of thecatheter tube and terminating coextensive the distal end portion of thecatheter tube, the second lumen extending longitudinally from theproximal end of the catheter tube and terminating proximal to the distalend portion of the catheter tube, said second lumen further comprisingadjacent said distal end a port hole extending through said outer wallmember, the first lumen being circular in cross-section and the secondlumen being crescent-shaped in cross-section and substantiallysurrounding the first lumen, the cross-sectional areas of the first andsecond lumens being approximately equal; (b) inserting within theproximal end of the first lumen a first support pin shaped to fit withinthe first lumen and inserting within the proximal end of the secondlumen a second support pin shaped to fit within the second lumen, thepins extending from the proximal end of the tube in a branchedconfiguration; (c) placing an extension tube over each of the supportpins of the branched configuration, each extension tube being inserted ashort distance within the proximal end of the lumen from which theunderlying support pin extends; (d) placing the dual lumen catheter withthe extension tubes and inserted support pins into an insert mold shapedto hold the catheter at the catheter distal end and to hold a softenedmaterial around a distal portion of the branched configuration of theextension tubes and pin supports extending from the catheter proximalend; (e) placing the softened material in the insert mold around thebranched configuration; (f) allowing the softened material to harden toform a branched hub integral with the catheter proximal end; and (g)thereafter removing the support pins from within the catheter and theextension tubes, thereby leaving channels which form the lumens, hub andextension tubes.
 5. The method as defined in claim 4 including the stepof fastening a luer fitting on the end of each of the extension tubesafter removal of the support pins.